Near-death experiences occur in life-threatening situations or situations which feel life-threatening, including in 10% of survived cardiac arrests. They are known from around the world, different epochs and various civilizations. Despite their mystic flavour, near-death experiences can be scientifically investigated. Research has revealed biological candidate mechanisms, including N-methyl-D-aspartate receptor hypofunction, REM sleep intrusion, migraine aura and an evolutionary model involving a survival benefit. This review explains the epidemiology, phenomenology and biological mechanisms of near-death experiences.